Multiple Episodes of Brecciation and Mineralization Associated with an Epizonal Granite Porphyry, True Hill, Southwestern New Brunswick

Abstract At True Hill in southwestern New Brunswick, low-grade porphyry-style Bi-Sn-Mo greisen mineralization is associated with the cupola of an epizonal granite porphyry (granite) that also exhibits three episodes of brecciation. The first episode of brecciation is an in situ, 8 m to 10 m wide transitional zone of net-veined to coarse-grained "blocky" endogranitic mesobreccia that is chlori-tized and greisenized and hosts weak disseminated mineralization. In a zone closer to the host rock-granite contact, angular fine- to coarse-grained endogranitic mesobreccia with greisenized matrix is superimposed on the earlier transitional breccia. The latest episode is fault-controlled and consists of quartz- and chalcedony-hosted subangular to rounded fine-grained "pebble" mesobreccias that crosscut and brecciate the other breccia types, as well as the adjacent altered metasedimentary country rocks. The first two episodes of brecciation are magmatic-hydrothermal in origin related to hydrofrac-turing of the granite carapace and are accompanied by greisenization and mineralization, whereas the post-mineralization, silica-hosted, "pebble" mesobreccias related to hydromagmatic, low-temperature fluid circulation and/or boiling along faults near the contact. These magmatic-hydrothermal and hydromagmatic mesobreccias are similar to those associated with W-Mo-Bi porphyry-greisen mineralization at the Mount Pleasant deposit.
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Summary: Breccias with angular and rounded clasts of a late-mineralization, "barren" hornblende ' porphyry dike set within a comminuted matrix consisting of rock fragments and quartz, cemented by quartz and K-feldspar of hydrothermal origin is observed in diamond drill cores from the Sar Cheshmeh porphyry copper deposit. Studies of age relationship between vein types, phyllic-altered clasts and the breccia groundmass suggest that the brecciation is a late event. The breccia clasts record evidence of...
Publication: Exploration & Mining Geology
Author(s): J. SHAHABPOUR
Issue: 1
Volume: 3
Year: 1994
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Summary: The Magino gold mine is located 45 km northeast of Wawa, Ontario. There was limited gold production in the late thirties. The present operation was officially opened in October 1988 and produced gold until September 1992. It was a 635 tonnes per day, decline-accessed mine, with ore coming from several small blast hole and shrinkage slopes.
The host for the gold is the Webb Lake granodiorite stock which was intruded into the Goudreau Lake Deformation Zone. This east-northeast-striking...
Publication: Exploration & Mining Geology
Author(s): ANTHONY J. DEEVY
Issue: 1
Volume: 3
Year: 1994
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Summary: The Ontario Geological Survey completed a regional till sampling project between 1984 and 1988 in the Black River Matheson (BRiM) area of northeastern Ontario. The project was designed to aid mineral exploration in the area by documenting the Quaternary stratigraphy and by providing a database of till geochemistry. This paper summarizes the results from the sonic overburden drilling component of the BRiM project carried out in areas of thick drift (> 5 m). Results from till sampling in areas...
Publication: Exploration & Mining Geology
Author(s): M.B. McCLENAGHAN
Issue: 1
Volume: 3
Year: 1994
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Summary: The Jinqingding gold deposit, situated in the east Jiaodong Peninsula of Shandong province, is typical of the pyrite-quartz vein gold deposits in the Muping-Rushan gold belt of China. The gold deposit is controlled by a great NNE fracture zone and is composed of several lenticular orebodies within the fracture zone occurring in the Kunyushan granite massif. The Kunyushan granite massif was formed by the replacement of the Archean Jiaodong group.
The main minerals associated with gold are...
Publication: Exploration & Mining Geology
Author(s): JIUHUA XU, WEIREN SUN, SHUIKU JIA
Issue: 1
Volume: 3
Year: 1994
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Summary: The Asturian fluorspar district consists of vein and stratiform deposits where mineralization is controlled by a combination of lithologjcal and tectonic factors.
It is postulated that these fluorspar deposits have been formed under disequilibrium conditions created during circulation of ascending hydrothermal solutions along faults and other high permeability conduits. Mixing of solutions is inferred from fluid inclusion studies. Cavity filling and replacement processes are very important in...
Publication: Exploration & Mining Geology
Author(s): JESUS GARCIA IGLESIAS, JORGE LOREDO
Issue: 1
Volume: 3
Year: 1994
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Summary: Cette etude porte sur I'alteration de la matiere organique et des argiles dans les boues carbonates devoniennes du facies "F" de la Formation de Pine Point et ses equivalents stratigraphiques la Formation d'Evie et 1'unite bitumineuse de la base de la Formation de Horn River. La matiere organique se compose principalement de bitume solide et de quelques fragments de fossiles (organo-clastes). La majorite des echantillons ne renferment que de 1'iDite et des interstratifiees illite/smectite.
Si...
Publication: Exploration & Mining Geology
Author(s): YVON HEROUX, ANDRE CHAGNON
Issue: 1
Volume: 3
Year: 1994
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Summary: Le gite de Pb-Zn de Gays River s'accompagne d'anomalies des proprietes de la matiere organique (MO) et des assemblages de mineraux d'argile (AMA). L'association entre la mineralisation, la distribution de la reflectance de la MO et des AMA suggere que ces traceurs peuvent servir a 1'exploration des sulfures de metaux de base dans cette region.
A l'emplacement du gite, la reflectance varie considerablement (0,8% a 1,88%), pouvant meme afficher une baisse avec 1'enfouissement, ce qui est...
Publication: Exploration & Mining Geology
Author(s): Y. HEROUX, A. CHAGNON, M.M. SAVARD
Issue: 1
Volume: 3
Year: 1994
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